DE 44 29 924 A1, which is incorporated by reference herein, discloses an underfloor structure for automobiles. Said underfloor structure of an automobile is provided such that the air resistance below the floor of the automobile is reduced, and the cooling performance for heat-radiating parts such as a transmission is improved. Here, the already-known underfloor structure has an underside cover by means of which a high-pressure region can be covered in the downward direction. Furthermore, from the already-known underfloor structure, it is known that the air stream flows from the front end of the automobile along an underside and generates cooling of the rear-axle transmission. A disadvantage of the already-known underfloor structure is that any change in the flow under the vehicle generates a change in the flow resistance coefficient, or impairs the flow resistance coefficient of the motor vehicle.
KR 10-0821141 B1, which is incorporated by reference herein, discloses an air-guiding plate for cooling a rear-axle differential. The already-known air-guiding plate is held by a spring. At elevated vehicle speed, the relative wind overcomes the spring force and pushes the already-known air-guiding plate downward, which leads to cooling of the rear-axle differential. Thus, when a certain vehicle speed is reached, the air-guiding plate is pushed downward and impairs the flow resistance coefficient, which is less advantageous specifically at an elevated vehicle speed.